®
Preliminary
SP6685
Charge Pump LED Driver For Camera Flash
FEATURES
VIN 1
10 VOUT
■ High Output Current Charge Pump: 700mA
C1 2
9 PGND
■ Adjustable FLASH mode
SP6685
■ x1 and x2 Automatic Modes for High Efficiency
8 SGND
C2 3
10 Pin DFN
■ Minimum External Components: No Inductors
7 FB
FLASH 4
■ High Frequency Operation: 2.4 MHz
6 RSET
EN 5
■ Low 50mV reference for low loss sensing
■ 1 µA shutdown current
Now Available in Lead Free Packaging
■ PWM Dimming Control
■ Over voltage protection on output
APPLICATIONS
■ Over current protection
■ LED Torch/Flash for Cell
■ Over temperature protection
Phones, DSCs, and Camcorders
■ Space Saving 10-pin 3mm x 3mm DFN
■ Generic Lighting/Flash/Strobe
Package
Applications
DESCRIPTION
The SP6685 is a current regulated charge pump ideal for powering high brightness LEDs for
camera flash applications. The charge pump can be set to regulate two current levels for
FLASH and TORCH modes. The SP6685 automatically switches modes between step-up
and step-down ensuring that LED current does not depend on the forward voltage. A low
current sense reference voltage (50mV) allows the use of small 0603 current sensing
resistors. The SP6685 is offered in 10-pin DFN package.
TYPICAL APPLICATION CIRCUIT
VIN
(2.7 - 4.3V)
CIN
4.7µF
VIN
CFC
1µF
TORCH/FLASH
ENABLE
®
VOUT
C1
SP6685 PGND
C2
SGND
FLASH
FB
RSET
EN
COUT
1µF
VREF = 50 - 150mV
RSET
88.7K
Date: 12/15/04
SP6685 Charge Pump LED Driver for Camera Flash
1
D1
1W LED
RSENSE
0.22Ω
© Copyright 2004 Sipex Corporation
ABSOLUTE MAXIMUM RATINGS
VIN - VOUT ....................................................................... -0.3V to 6V
Output Current Pulse (Flash) ................................. 1A
Output Current Continuous (Torch) ..................... 0.4A
Storage Temperature ...................... -65°C to +150°C
Operating Temperature ..................... -40°C to +85°C
EN ................................................................ 0V to 7V
ESD. ........................................................... 2kV HBM
These are stress ratings only and functional operation of
the device at these ratings or any other above those
indicated in the operation sections of the specifications
below is not implied. Exposure to absolute maximum
rating conditions for extended periods of time may affect
reliability.
ELECTRICAL CHARACTERISTICS
TA = -40°C to +85°C, VIN =3.6, CIN = 4.7µF, CFC = COUT = 1.0µF. VSHDN = VIN, typical values at 25°C. The ♦ denotes the
specifications which apply over the full operating range unless otherwise noted.
PARAMETER
Operating Input Voltage
MIN.
TYP.
2. 7
Quiescent Current
0. 5
MAX.
UNITS
CONDITIONS
4.3
V
♦
2
mA
♦
VIN = 2.7 - 4.3V FLASH = 0V,
Iload = 100µA
FLASH = VIN, 2x mode
2
µA
♦
2.4
MHz
♦
Charge Pump Equivalent
Resistance (x2 mode)
5
Ω
VFB = 0V, VIN= 3.6V
Charge Pump Equivalent
Resistance (x1 mode)
0.6
0.8
Ω
VIN= 3.6V
Shutdown Current
1
Oscillator Frequency
VIN = 4.3V, VEN = 0V
FB Reference Voltage
142
150
158
mV
♦
FLASH = VIN RSET = 100K
FB Reference Voltage
45
50
55
mV
♦
FLASH = GND
FB Pin Current
0. 5
µA
♦
VFB = 1V
EN, FLASH Logic Low
0.4
V
♦
V
♦
0.5
µA
♦
500
µs
♦
EN, FLASH Logic High
1.3
EN, FLASH Pin Current
VOUT Turn-on Time
250
Thermal Shutdown
Temperature
145
ºC
Thermal Hysteresis
10
ºC
Date: 12/15/04
SP6685 Charge Pump LED Driver for Camera Flash
2
VIN = 3.6V, FB within 90% of
regulation
© Copyright 2004 Sipex Corporation
PIN DESCRIPTION
PIN NUMBER
PIN NAME
1
VIN
Input Voltage for the charge pump. Decouple with 1µF ceramic
capacitor close to the pins of the IC.
2
C1
Positive input for the external fly capacitor. Connect a ceramic 1µF
capacitor close to the pins of the IC.
3
C2
Negative input for the external fly capacitor. Connect a ceramic 1µF
capacitor close to the pins of the IC.
4
FLASH
Logic input to toggle operation between FLASH and TORCH mode.
In TORCH mode FB is regulated to the internal 50mV reference. In
FLASH mode FB reference voltage can be adjusted by changing the
resistor from RSET pin to ground. Choose the external current sense
resistor (RSENSE) based on desired current in TORCH mode. The
FLASH mode should be limited to 200ms to avoid overheating the
charge pump.
5
EN
Shutdown control input. Connect to VIN for normal operation, connect
to ground for shutdown.
6
RSET
Connect a resistor from this pin to ground. When in FLASH mode
(FLASH = High) this resistor sets the current regulation point
according to the following: VFB = (1.26V/ RSET)*11.2KΩ.
7
FB
Feedback input for the current control loop. Connect directly to the
current sense resistor.
8
SGND
Internal ground pin. Control circuitry returns current to this pin.
9
PGND
Power ground pin. Fly capacitor current returns through this pin.
10
VOUT
Charge Pump Output Voltage. Decouple with an external capacitor.
At least 1uF is recommended. Higher capacitor values reduce output
ripple.
Date: 12/15/04
DESCRIPTION
SP6685 Charge Pump LED Driver for Camera Flash
3
© Copyright 2004 Sipex Corporation
TYPICAL PERFORMANCE CHARACTERISTICS
Torch Mode 200mA Iout
300
Flash Mode 700mA Iout
900
800
700
200
Iout (mA)
Iout (mA)
600
Vf = 3.0V
Vf = 3.3V
Vf = 3.6V
100
500
Vf = 3.3V
400
Vf = 3.6V
300
Vf = 3.9V
Vf = 3.9V
Vf = 4.2V
200
100
0
0
3.0
3.2
3.4
3.6
Vin (V)
3.8
4.0
4.2
3.0
Figure 1. Torch Mode Output Current
3.4
90
4.0
4.2
Vf = 3.3V
Vf = 3.6V
Vf = 3.9V
Vf = 4.2V
90
Efficiency (%)
80
Vf = 3.0V
Vf = 3.3V
Vf = 3.6V
Vf = 3.9V
60
3.8
Flash Mode 700mA Efficiency
100
70
3.6
Vin (V)
Figure 2. Flash Mode Output Current
Torch Mode 200mA Efficiency
100
Efficiency (%)
3.2
50
80
70
60
50
40
40
3.0
3.2
3.4
3.6
Vin (V)
3.8
4.0
4.2
3.0
Figure 3. Torch Mode Efficiency
Date: 12/15/04
3.2
3.4
3.6
Vin (V)
3.8
4.0
4.2
Figure 4. Flash Mode Efficiency
SP6685 Charge Pump LED Driver for Camera Flash
4
© Copyright 2004 Sipex Corporation
TYPICAL PERFORMANCE CHARACTERISTICS
Ch1 = EN
Ch1 = EN
Ch2 = VOUT
Ch4 = lin
Ch2 = VOUT
(0.5A/div)
Ch4 = lin
(0.5A/div)
Figure 5. Startup 200mA Torch,
VIN = 3.6V, VOUT = 3.2V
Figure 6. Startup 700mA Flash,
VIN = 3.6V, VOUT = 3.6V
Ch1 = VIN (AC)
Ch1 = VIN (AC)
50mA/div
50mA/div
Ch2 = VOUT
Ch2 = VOUT (AC)
(AC) 50mA/div
50mA/div
Figure 8. Ripple 700mA Flash, VIN = 3.6V,
VOUT = 3.6V.
Figure 7. Ripple 200mA Torch, VIN = 3.6V,
VOUT = 3.2V.
Date: 12/15/04
SP6685 Charge Pump LED Driver for Camera Flash
5
© Copyright 2004 Sipex Corporation
FUNCTIONAL DIAGRAM
CLK
RSET BLOCK
RSET 6
+
RSET
{ }
1.26V
V= RSET
RSET REF
BG REF
+
- 1.25V
RESISTOR
TAPS
FB REF
1
MUX
2x1
50mV 0 s
+
-
FB 7
FB COMP
FB
COM P
SGN 8
SET
DOMIANT
S
0
ONE
SHOT
x11.2kohms
FLASH 4
FLASH=1, S=1, RSET REF
FLASH=0, S=0, 50mV
COUNTER
32 COUNT
CLR
R
EN 5
VIN 1
MODE SWITCH
0 =1X
1=2X
135C ON
THERMAL FAULT
OVER TEMP COMP
145C OFF
2.4MHZ
CLK
CHARGE
PUMP
SWITCHES
C1
C2
VOUT
CLK
PGND
THEORY OF OPERATION
The SP6685 also has two modes of operation to control the output current, the 1X
mode and 2X mode. Operation begins after
the enable pin EN receives a logic high, the
bandgap reference wakes up after 200µsec,
and then SP6685 goes through a soft-start
mode designed to reduce inrush current.
The SP6685 starts in the 1X mode, which
acts like a linear regulator to control the
output current by continuously monitoring
the feedback pin FB. In 1X mode, if the
SP6685 auto detects a dropout condition,
which is when the FB pin is below the
The SP6685 is a charge pump regulator
designed for converting a Li-Ion battery
voltage of 2.7V to 4.2V to drive a white LED
used in digital still camera Flash and Torch
applications. The SP6685 has two modes
of operation which are pin selectable for
either Flash or Torch. Flash mode is usually
used with a pulse of about 200 to 300
milliseconds to generate a high intensity
Flash. Torch can be used continuously at a
lower output current than Flash and is often
used for several seconds in a digital still
camera “movie” mode.
Date: 12/15/04
SP6685 Charge Pump LED Driver for Camera Flash
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© Copyright 2004 Sipex Corporation
THEORY OF OPERATION
regulation point for more than 32 cycles of
the internal clock, the SP6685 automatically switches to the 2X mode. The SP6685
remains in the 2X mode until one of four
things happens: the enable pin EN has
been toggled, the Flash pin has changed
from high to low, VIN is cycled or a thermal
fault occurs. The 2X mode is the charge
pump mode where the output can be pumped
as high as two times the input voltage,
provided the output does not exceed the
maximum voltage for the SP6685, which is
internally limited to about 4.3V. In the 2X
mode, as in the 1X mode, the output current
is regulated by the voltage at the FB pin.
When in Flash mode, (Flash = VIN), the FB
regulation voltage is set by the resistor RSET
connected between the RSET pin and SGND
and the equation:
VFB = (1.26V/ RSET)*11.2KΩ (Flash Mode)
Where 1.26V is the internal bandgap reference voltage and 11.2KΩ is an internal
resistance used to scale the RSET current.
Typical values of RSET are 100K to 500K for
a range of VFB = 150mV to 30mV in Flash
mode.
The output current is then set in either Flash
or Torch mode by the equation:
In the Torch mode, (Flash = GND) the Flash
pin is set to logic low and the SP6685 FB pin
regulates to 50mV output:
IOUT = VFB / RSENSE
VFB = 50mV (Torch Mode)
OVERTEMPERATURE PROTECTION
When the temperature of the SP6685 rises above 145 degrees Celsius, the over temperature
protection circuitry turns off the output switches to prevent damage to the device. If the
temperature drops back down below 135 degrees Celsius, the part automatically recovers
and executes a soft start cycle.
OVERVOLTAGE PROTECTION
The SP6685 has over voltage protection. If the output voltage rises above the 4.3V threshold,
the over voltage protection shuts off all of the output switches to prevent the output voltage
from rising further. When the output decreases below 4.3V, the device resumes normal
operation
OVERCURRENT PROTECTION
The over current protection circuitry monitors the average current out of the VOUT = 50mV
(Torch Mode) pin. If the average output current exceeds approximately 1Amp, then the over
current protection circuitry shuts off the output switches to protect the chip.
Date: 12/15/04
SP6685 Charge Pump LED Driver for Camera Flash
7
© Copyright 2004 Sipex Corporation
COMPONENT SELECTION
Once the RSENSE resistor has been selected
for Torch mode, the VFB voltage can be
selected for Flash mode using the following
equation:
The SP6685 charge pump circuit requires 3
capacitors: input, output and fly capacitor,
and a 1µ F value is typically recommended.
For the input capacitor, a larger value of
2.2µ F or 4.7µ F will help reduce input voltage ripple for applications sensitive to ripple
on the battery voltage. All the capacitors
should be ceramic to obtain low ESR, which
improves bypassing on the input and output
and improves output voltage drive by reducing output resistance. X5R or X7R Ceramic
capacitors are recommended for most applications. A selection of recommended
capacitors is included in Table 1. The input
and output capacitors should be located as
close to the VIN and VOUT pins as possible to
obtain best bypassing, and the returns
should be connected directly to the PGND pin
or to the thermal pad ground located under
the SP6685. The fly capacitor should be
located as close as possible to the C1 and
C2 pins as possible.
VFB = IOUT *RSENSE (Flash Mode) where IOUT is
for Flash Mode
Next, the RSET resistor can be selected for
Flash mode using the following equation:
RSET = (1.26V/ VFB)*11.2KΩ (Flash Mode)
For an example of 200mA Torch mode and
600mA Flash mode, the values RSENSE =
0.25Ω, VFBREF = 150mV (Flash Mode), and
RSET = 88.7K are calculated. The power
obtained in the Flash mode would be:
PFLASH = VFB *IOUT = 150mV*600mA = 90mW.
The typical 0603 surface mount resistor is
rated 1/10 watt continuous power and 1/5
watt pulsed power, more than enough for
this application. For other applications, the
PFLASH can be calculated from the resistor
size selected. The RSENSE resistor is recommended to be size 0603 for most applications.
The sense resistor Rsense is determined by
the value needed in the Torch mode for the
desired output current by the equation:
RSENSE = VFB / IOUT where VFB = 50mV (Torch
Mode)
Part Reference
Part Number
Value
Size
Manufacturers/ Website
U1
SP6685ER
3x3mm DFN - 10 pin Sipex/www.sipex.cpm
CIN
GRM188R0J475KE19
4.7uF/6.3V 0603/X5R/0.9mm ht Murata/www.murata.com
COUT, CF
GRM155R60J105KE19B 1uF/6.3V 0402/X5R/0.5mm ht Murata/www.murata.com
RSET
88.7K
0402
any
RSENSE
0.22ohms
0603
any
Date: 12/15/04
SP6685 Charge Pump LED Driver for Camera Flash
8
© Copyright 2004 Sipex Corporation
PACKAGE: 10 PIN DFN
D
A3
D/2
E/2
E
A1
Top View
A
Side View
D2
3x3 10 Pin DFN JEDEC MO-229 (VEED-5)
VARIATION
MIN
NOM
MAX
SYMBOL
A
0.8
0.9
1
A1
0
0.02
0.05
A2
0.55
0.65
0.8
0.20 REF
A3
b
0.18
0.25
0.3
2.00 BSC
D
D2
2.2
2.7
0.5 PITCH
e
3.00 BSC
E
E2
1.4
1.75
K
0.2
L
0.3
0.4
0.5
1
E2
K
L
b
e
Bottom View
Note: Dimensions in (mm)
Date: 12/15/04
2
SP6685 Charge Pump LED Driver for Camera Flash
9
© Copyright 2004 Sipex Corporation
ORDERING INFORMATION
Part Number
Operating Temperature Range
Package Type
SP6685ER .................................................. -40°C to +85°C ........................................................... 10 Pin DFN
SP6685ER/TR ............................................ -40°C to +85°C .......................................................... 10 Pin DFN
Available in lead free packaging. To order add “-L” suffix to part number.
Example: SP6685ER/TR = standard; SP6685ER-L/TR = lead free
/TR = Tape and Reel
Pack quantity is 3,000 for DFN.
CLICK HERE TO ORDER SAMPLES
Corporation
ANALOG EXCELLENCE
Sipex Corporation
Headquarters and
Sales Office
233 South Hillview Drive
Milpitas, CA 95035
TEL: (408) 934-7500
FAX: (408) 935-7600
Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the
application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others.
Date: 12/15/04
SP6685 Charge Pump LED Driver for Camera Flash
10
© Copyright 2004 Sipex Corporation